The AnoRep project targets the reproductive biology of An. gambiae mosquitoes, to provide a deeper knowledge of the processes regulating reproduction in this species, to identify novel targets and to develop innovative approaches for the control of natural populations. In this project we will remarkably improve the understanding of reproductive processes occurring in Anopheles mosquitoes, bringing current knowledge considerably beyond the state-of-the-art, and we will translate this knowledge into tools for the fight against malaria.
In An. gambiae mating occurs in swarms that are formed at dusk and that comprise a few tens to a few hundred males. Females enter the swarm, are grabbed by a male and the mating couple leaves the swarm while still in copulation. The whole process lasts approximately 20 seconds, during which males transfer sperm, which will be stored in a dedicated sperm storage organ named spermatheca, and secretions from their male accessory glands (MAGs) in the form of a gelatinous rod generally referred to as the mating plug.
Figure 1. The reproductive tracts of male and female An. gambiae. A. The male reproductive tract, showing the testes (T) and male accessory glands (MAG). B. The reproductive tract of a freshly mated female, showing the ovaries (Ov), the atrium (A) in which a mating plug (Plug) is visible, and the spermatheca (Sp, also shown in the inset, where the glandular cells surrounding the capsule are visible).
The occurrence of mating induces a series of behavioral and physiological responses in females, which include enhanced ovulation (the release of oocytes from the ovaries) and oviposition (the process of egg laying), and induction of refractoriness to further mating. An. gambiae females indeed mostly mate only once in their lifetime. This makes copulation an extremely vulnerable step in the mosquito lifecycle, and a good target for intervention strategies aimed at reducing or eradicating natural mosquito populations. Indeed interfering with the outcome of mating (for instance by preventing swarms from gathering, males from being fertile or females from storing viable sperm) would have a strong impact on the size of natural populations.
The AnoRep project focuses on the analysis of three major players of mosquito fertility: MAGs, sperm, and spermatheca, in both laboratory and field settings. This information will be used to set the scene for the identification of inhibitors of mosquito fertility. The three objectives are:
1) Unravelling the role of the MAGs in Anopheles fertility
Our recent studies have taken the analysis of the role of the MAGs in Anopheles to the molecular level, and we have identified a number of important male reproductive factors. In this objective, we will build on the ongoing analyses of the function of single MAG proteins to focus our studies on the identification of the processes that are occurring in these male reproductive organs and that may be at the centre of mosquito reproduction.
2) Identification of factors and processes involved in sperm viability and function
In this objective, we will unravel the processes that warrant sperm viability for the female lifetime and that secure successful fertilization. This will be achieved by a comprehensive analysis of the sperm and the female sperm storage organ, which will provide novel insights of the factors and mechanisms regulating sperm function in Anopheles.
3) Towards the manipulation of mosquito reproductive success in the field
In this objective we propose to use the information that we will have collected in the laboratory analyses and confirmed in the field studies, to go back to the bench with the aim to develop novel tools to interfere with the reproductive ability of field mosquitoes.
The results obtained in the AnoRep project will provide a tremendous contribution to the knowledge of reproductive biology in Anopheles mosquitoes. The knowledge gained here will be translated into novel ideas, concepts and tools for attempting reduction/eradication of natural mosquito populations with the view to reduce malaria transmission, complementing and strengthening already available strategies in integrated control campaigns. The identification of factors and mechanisms shaping reproductive success will be instrumental for the development of transgenic mosquitoes in which specific factors could be over-expressed, knocked-down or mis-expressed to induce sterility in male and female individuals. These genetically modified mosquitoes could eventually be used in control programs such as those based on the release of sterile insects to wipe out field populations (sterile insect technique).
This research is anticipated to open novel crucial opportunities for the control of these and other insect vectors of human disease, providing a tremendous contribution to the armory of weapons already available. The results will be disseminated at conferences, seminar, interviews with local and national broadcasters, through publications and other communication means.